Wrist-mounted electrocardiography device

ABSTRACT

Wearable devices are described herein including a housing and a mount configured to mount the housing to a wrist of a wearer. The wearable devices further include first and second electrical contacts configured such that the first electrical contact is in contact with skin proximate of the wrist when the wearable device is so mounted. The second electrical contact is disposed on a surface of the wearable device away from the wrist such that, when the wearer contacts the second electrical contact with a finger or other element of the arm opposite the wrist, an electrocardiographic waveform of the wearer can be extracted from voltage fluctuations between the first and second electrodes. Such wearable devices can be used for periodic logging or other applications of the electrocardiographic waveforms of the wearer. Such logged electrocardiographic waveforms could be used to determine a medical or health state of the wearer.

BACKGROUND

Unless otherwise indicated herein, the materials described in thissection are not prior art to the claims in this application and are notadmitted to be prior art by inclusion in this section.

Electrocardiography (ECG) is a technique that records electricalactivity of the heart by measuring electrical signals from two or morepoints on the skin. The measurements result in one or more waveforms(electrocardiograms) that are related to the beating of the heart. Thewaveforms may also include other features that may be indicative ofheart health, abnormalities, or medical conditions. Theelectrocardiographic measurements can be obtained by placing electrodeson the skin at multiple body locations (e.g., on the chest, arms, and/orlegs) and electrically connecting the electrodes to a heart monitor orother electronic measurement device. Typically, electrocardiograms areobtained in clinical settings in which a physician, nurse, or othermedical professional is involved in placing the electrodes on the bodyand operating the heart monitor.

SUMMARY

Some embodiments of the present disclosure provide a wearable deviceincluding: (i) a housing; (ii) a mount configured to mount the housingto a first external body surface, wherein the first external bodysurface is a wrist location of a first arm of a wearer; (iii) a firstelectrical contact disposed on the housing, wherein the first electricalcontact is configured to contact skin at the first external body surfacewhen the housing is mounted on the first external body surface; (iv) asecond electrical contact, wherein the second electrical contact isconfigured to be contacted by skin of a second external body surface,wherein the second external body surface is a location of a second armof the wearer; and (v) a signal conditioner disposed in the housing andelectrically connected to the first and second electrical contacts,wherein the signal conditioner is configured to extract anelectrocardiographic waveform from voltage fluctuations between thefirst electrical contact and the second electrical contact.

Some embodiments of the present disclosure provide a wearable deviceincluding: (i) a housing; (ii) means for mounting the housing to a firstexternal body surface, wherein the first external body surface is awrist location of a first arm of a wearer; (iii) a first electricalcontact disposed on the housing, wherein the first electrical contact isconfigured to contact skin at the first external body surface when thehousing is mounted on the first external body surface; (iv) a secondelectrical contact, wherein the second electrical contact is configuredto be contacted by skin of a second external body surface, wherein thesecond external body surface is a location of a second arm of thewearer; and (v) means for extracting an electrocardiographic waveformfrom voltage fluctuations between the first electrical contact and thesecond electrical contact.

Some embodiments of the present disclosure present a method including:(i) mounting a wearable device to a wrist location of a first arm of awearer, wherein the device comprises: (a) a housing; (b) a mountconfigured to mount the housing to the wrist location; (c) a firstelectrical contact disposed on the housing, wherein the first electricalcontact is configured to contact skin at a first external body surfacewhen the housing is mounted on the first external body surface; (d) asecond electrical contact, wherein the second electrical contact isconfigured to be contacted by skin of a second external body surface,wherein the second external body surface is a location of a second armof the wearer; and (e) a signal conditioner disposed in the housing andelectrically connected to the first and second electrical contacts,wherein the signal conditioner is configured to extract anelectrocardiographic waveform from voltage fluctuations between thefirst electrical contact and the second electrical contact; (ii) whilethe wearable device is mounted to the wrist location of the first arm ofthe wearer such that the first electrical contact is in contact withskin at the first external body surface, placing skin of the secondexternal body surface in contact with the second electrical contact; and(iii) while the first electrical contact is in contact with skin at thefirst external body surface and the second electrical contact is incontact with skin of the second external body surface, using the signalconditioner to extract the electrocardiographic waveform.

These as well as other aspects, advantages, and alternatives, willbecome apparent to those of ordinary skill in the art by reading thefollowing detailed description, with reference where appropriate to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a view of a person wearing an example wearable device.

FIG. 1B is a view of the person and wearable device illustrated in FIG.1A, when the user is contacting an electrical contact of the wearabledevice with a finger.

FIG. 2 is a diagram illustrating an example electrical model of elementsof the person and wearable device illustrated in FIGS. 1A and 1B.

FIG. 3A is a perspective view of an example wearable device.

FIG. 3B is a perspective view of an example wearable device.

FIG. 3C is a perspective view of an example wearable device.

FIG. 3D is a perspective view of an example wearable device.

FIG. 4A is a top perspective view of elements of an example wearabledevice.

FIG. 4B is a bottom perspective view of the elements of the examplewearable device illustrated in FIG. 4A.

FIG. 4C is a bottom perspective view of the elements of the examplewearable device illustrated in FIG. 4A, when a housing and a frame ofthe elements are disengaged from each other.

FIG. 4D is a top perspective view of the housing of the elements of theexample wearable device illustrated in FIG. 4A.

FIG. 4E is a bottom perspective view of the frame of the elements of theexample wearable device illustrated in FIG. 4A.

FIG. 4F is an exploded top perspective view of the frame of the elementsof the example wearable device illustrated in FIG. 4A.

FIG. 5 is a block diagram of an example system that includes a pluralityof wearable devices in communication with a server.

FIG. 6 is a functional block diagram of components disposed in anexample wearable device.

FIG. 7 is a flowchart of an example method.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying figures, which form a part hereof. In the figures, similarsymbols typically identify similar components, unless context dictatesotherwise. The illustrative embodiments described in the detaileddescription, figures, and claims are not meant to be limiting. Otherembodiments may be utilized, and other changes may be made, withoutdeparting from the scope of the subject matter presented herein. It willbe readily understood that the aspects of the present disclosure, asgenerally described herein, and illustrated in the figures, can bearranged, substituted, combined, separated, and designed in a widevariety of different configurations, all of which are explicitlycontemplated herein.

I. Overview

A wearable device may be configured to measure one or more physiologicalparameters of the wearer. The one or more physiological parameters caninclude an electrocardiographic waveform (ECG), which may be related tothe electrical activity of the wearer's heart and, thus, a medicaland/or health state of the wearer. To measure an ECG waveform, thewearable device may include two electrical contacts that can be placedin contact with the wearer's skin at respective locations such as thewearer's wrist(s), forearm(s), upper arm(s), leg(s), thigh(s), etc. Forexample, first and second electrical contacts could contact skin on theleft and right arms of the wearer, respectively (e.g., skin at the leftand right wrists of the wearer, skin at the left wrist and right indexfinger of the wearer, etc.), and the ECG waveform may be extracted fromvoltage fluctuations between the first and second electrical contacts.One or more properties of a detected ECG waveform and/or of a pluralityof detected ECG waveforms (detected, e.g., during a plurality ofrespective periods of time) could be determined and/or related to one ormore physiological and/or health states of the wearer.

In some examples, the wearable device includes a housing (e.g., awater-resistant and/or water-proof housing) and a mount (e.g., a band)that can mount the housing on a particular external body location, suchas a wrist of a first arm of the wearer (i.e., a first external bodysurface). The first electrical contact may protrude from a side of thehousing facing the skin at the wrist location of the first arm, suchthat the first electrical contact contacts the skin of the wristlocation when the housing is mounted on the wrist. The second electricalcontact could be configured to be contacted by skin at a location on asecond arm of the wearer (e.g., skin of a finger, hand, wrist, or otherlocation on the arm of the wearer opposite the arm to which the wearabledevice is mounted). For example, the second electrical contact could bedisposed on an outside surface of the housing and/or the mount (e.g., anoutside surface of a band used to mount the wearable device to the wristof the first arm) such that the wearer could move his or her second arm(i.e., the arm opposite the arm to which the wearable device is mounted)to touch the second electrical contact without the second arm being inelectrical contact with the first arm. When the wearable device isoperated in this way, a signal conditioner or other electronics of thewearable device may extract an ECG waveform from voltage fluctuationsbetween the first and second electrical contacts. The wearable devicecould be used to extract such ECG waveforms while the wearer is involvedin certain activities (e.g., while running or engaged in other forms ofexercise) or throughout the day. Thus, the wearable device mayfacilitate repeated and/or near-continuous cardiac monitoring. Suchcardiac monitoring could allow the detection of rare events (e.g.,arrhythmias, transient bradycardia and/or tachycardia), cardiacelectrical activity during a wider range of wearer behaviors than occurin a hospital or other controlled medical setting, the detection ofchanges in the electrical activity of the heart over protracted (e.g.,weeks, months) periods of time, or other properties of the physiologicalstate of a wearer.

The electronics of the wearable device may include a signal conditioner,a microprocessor, an analog-to-digital converter (which may be part ofthe microprocessor), data storage, a wireless transmitter, and/or othercomponents. The signal conditioner may be electrically connected to thefirst and second electrical contacts and may be configured to extract anECG waveform from voltage fluctuations between the electrical contacts.The signal conditioner may, for example, include at least one amplifier,at least one high-pass filter, and at least one low-pass filter. Themicroprocessor may obtain data related to the electrocardiographicsignal (e.g., after the signal is digitized by the analog-to-digitalconverter), and the microprocessor may use the wireless transmitter totransmit the data related to the ECG waveform to a remote computingdevice (e.g., to the “cloud”). Additionally or alternatively, themicroprocessor may log the data related to the ECG waveform in the datastorage. In some examples, the electronics (e.g., the signalconditioner) includes circuitry or other elements configured to detectthat the first and second electrical contacts are contacting skin and/orthat an ECG waveform may be extracted from voltage fluctuations betweenthe electrical contacts. The wearable device may be operated relative tosuch a determination; for example, an ECG waveform may be extractedusing the signal conditioner and logged, transmitted, or used in someother way in response to the determination that the first and secondelectrical contacts are in contact with skin at respective first andsecond skin locations.

The first and second electrical contacts (and any further electricalcontacts) of the wearable device could be configured in a variety ofways to allow the extraction of an ECG waveform from voltagefluctuations between the electrical contacts under a range ofphysiological and environmental conditions. The electrodes could have avariety of surface compositions to allow ohmic and/or capacitiveelectrical coupling between the electrodes and skin locations of awearer. Such surface compositions could include stainless steel, gold,platinum, silver, silver/silver-chloride, polymers or rubbers containingconductive particles, or other conductive or partially conductivematerials. Further, the shape and/or surface texture of the electrodescould be specified to allow electrical contact with skin. In someexamples, the electrodes could be configured to have a substantiallycapacitive electrical contact with skin; e.g., the electrodes couldinclude a flat conductor having a substantially nonconductive dielectriccoating configured to be in contact with skin. Other compositions andconfigurations of electrodes are anticipated.

The wearable device could include further sensors. In some examples,this could include the wearable device having additional electricalcontacts configured to provide additional electrophysiological signals(e.g., EMG signals) or other information (e.g., skin resistance,Galvanic skin response). Further sensors could include temperaturesensors, light sensors, galvanic sensors, proximity sensors, GPSsensors, accelerometers, or other sensors or combinations of sensors. Insome examples, the device could include a photoplethysmographic sensoror some other sensor(s) configured to detect a volume and/or a change inthe volume of blood in subsurface vasculature of a wearer. Such detectedinformation could be used, in combination with an extracted ECGwaveform, to determine one or more properties of the heart and/orvasculature of the wearer. For example, a diastolic, systolic, or otherblood pressure of the wearer could be determined.

In some examples, the wearable device may include a user interface thatis configured to provide user-discernible indications (e.g., visual,audible, and/or tactile indications) of one or more physiologicalparameters measured and/or determined by the device. For example, theuser interface could indicate an ECG waveform extracted using the firstand second electrical contacts during a period of time when the user iscontacting the second electrode with, e.g., a finger of an arm oppositethe arm to which the wearable device is mounted. In some examples, theuser interface could additionally provide a means for one or moresettings of the wearable device (e.g., a frequency at which to operatethe user interface to indicate that the user should contact the secondelectrical contact with, e.g., a finger of the opposite arm) to bespecified by a wearer according to the wearer's preferences. In someexamples, the wearable device may include a wireless communicationinterface that can transmit data to an external device, for example,using Bluetooth, ZigBee, WiFi, and/or some other wireless communicationprotocol. The data transmitted by the wireless communication interfacemay include data indicative of one or more physiological parametersmeasured by the device, such as extracted ECG waveforms.

It should be understood that the above embodiments, and otherembodiments described herein, are provided for explanatory purposes, andare not intended to be limiting.

Further, the term “medical condition” as used herein should beunderstood broadly to include any disease, illness, disorder, injury,condition or impairment—e.g., physiologic, psychological, cardiac,vascular, orthopedic, visual, speech, or hearing—or any situationrequiring medical attention.

II. ECG Performed Between the Arms of a Wearer

The heart creates an electric field within the body during the processof pumping blood. The temporal and spatial properties of this field arerelated to the sum of a plurality of ionic currents that flow within theheart as a result of the depolarization and repolarization ofelectrically active cells of the heart (e.g., cardiomyocytes) duringactivity of the heart (e.g., during a heartbeat). This electric fieldwithin the body results in voltage fluctuations at the skin (and otherlocations within the body) being related at least in part to theelectrical activity of the heart. As a result, measurement of thesevoltage fluctuations could be used to detect and/or determineinformation about the activity of the heart, e.g., to determine a healthor medical state (e.g., a disease state) of the heart.

An electrocardiographic (ECG) waveform can be extracted from voltagefluctuations between two (or more) location on the skin of a person(e.g., by using electrodes to grant a measurement device electricalaccess to the two or more skin locations). ECG waveforms can beextracted from pairs of skin locations on a person, such as between theleft and right arms, between the right arm and left leg, and between theleft arm and left leg. ECG waveforms can also be extracted fromcombinations of voltage fluctuations at more than two skin locations;for example, an ECG waveform could be generated based on the differencebetween the voltage at a first electrode (e.g., an electrode over theheart) and a mean of the voltages of a set of other electrodes (e.g., amean over the voltages of electrodes at the right arm, left arm, andleft leg).

Further, an extracted ECG waveform corresponding to a particularheartbeat generally includes a number of temporal features correspondingto phases of the activity of the heart during the particular heartbeat.Specifically, such an extracted ECG waveform may include a P wave(corresponding to depolarization of the atria of the heart), QRS complex(corresponding to depolarization of the ventricles of the heart), and aT wave (corresponding to repolarization of the ventricles). Such anextracted ECG waveform may include additional features (e.g., a U wave)and/or lack features (e.g., the T wave) according to a medical state ofa person, an anatomical or physiological property of the person, and/orthe properties of the electrodes and/or measurement equipment used toextract the ECG waveform. One or more properties of the extracted ECGwaveform (e.g., a Q-T interval, an R-R interval, a P-R interval, an S-Tinterval, a Q-T interval, an amplitude and/or polarity of a T-wave, andamplitude, polarity, or some other parameter(s) of some other aspect ofthe ECG waveform) could be determined and used to determine a medicaland/or health state of the heart and/or of the person containing theheart (e.g., a metabolic rate, a degree of physical exertion, anelevated or depressed level of one or more electrolytes, coronaryischemia, heart attack, cardiac hypertrophy, the presence of certaindrugs and/or toxins).

A wearable device could be configured to extract one or more ECGwaveforms from skin of a wearer by measuring voltage fluctuationsbetween two or more skin locations of the wearer. This could includeaccessing the voltage fluctuations at the two or more skin locations byapplying respective two or more electrical contacts or electrodes to thetwo or more skin locations, and electrically connecting the two or moreelectrical contacts or electrodes to a signal conditioner or otherelectrical measurement device of the wearable device. This connectioncould include long flexible leads connecting between a particular skinlocation to the wearable device, which could be located at some otherlocation on or near the body of the wearer (e.g., the wearable devicecould be connected to a belt worn by the wearer, and leads could runfrom the belt location to electrical contacts at two skin locations atthe wrists of the wearer). Additionally or alternatively, two or moreelectrical contacts could be disposed on the wearable device andconfigured to contact respective two or more skin locations. The two ormore skin locations could be proximate to each other (e.g., the wearabledevice could be mounted to a wrist of the wearer, and the two skinlocations could be skin location on the wrist of the wearer).Alternatively, the two or more skin locations could be distant locationsand the wearer could move skin locations of the wearer's body to contactelectrical contacts of the wearable device.

As an example, a wearable device could be configured to mount to a firstwrist (e.g., the left wrist) of the wearer and to have a firstelectrical contact configured to contact a first skin location on thefirst wrist. The wearable device could further include a secondelectrical contact configured to be contacted by a second skin locationof the wearer. That is, the wearer could move a portion of the wearer'sbody (e.g., a right hand) proximate to the wearable device such that asecond skin location (e.g., a finger, hand, or wrist location of the armof the wearer opposite the arm to which the wearable device is mounted)is in contact with the second electrical contact of the wearable device.In this way, the wearable device could enable periodic extraction of ECGwaveforms from voltage fluctuations between the two skin locations(e.g., between a wrist location of the left arm and a finger location ofthe right arm). Such a wearable device could be configured in the formof a wristwatch or other wrist-mounted device (i.e., having a centralhousing (on or within which could be mounted first and/or secondelectrical contacts) mounted to the wrist by e.g., a strap or bandconfigured to encircle the wrist) and could include means for performingadditional functions, e.g., indicating a time and/or information aboutextracted ECG waveforms to the wearer.

FIG. 1A illustrates such an example wearable device 110 mounted to awrist of a first arm 105 a of a wearer 100 during a first period oftime. The wearable device 110 includes a housing 120 mounted to thewrist of the first arm 105 a by a mount 140 (e.g., a strap or band). Thewearable device further includes first (not shown) and second 130electrical contacts. The first electrical contact is disposed on aninside (i.e., wrist-facing) side of the housing 120 and configured tocontact skin at a first external body surface (i.e., skin of the wristof the first arm 105 a) when the housing 120 is mounted on the wrist ofthe first arm 105 a. The second electrical contact 130 is configured tobe contacted by skin of a second external body surface (e.g., by finger,hand, wrist, or other skin of a second arm 105 b of the wearer 100). Thewearable device 110 additionally includes electronics (e.g., a signalconditioner, not shown) electrically connected to the first and second130 electrical contacts and configured to extract an ECG waveform(related to the electrical activity of the heart 101 of the wearer 100)from voltage fluctuations between the first and second 130 electricalcontacts.

FIG. 1B illustrates the wearable device 110 and wearer 100 during asecond period of time when the wearer 100 is positioning skin of afinger of the second arm 105 b in contact with the second electricalcontact 130. In this state, electronics (e.g., a signal conditioner) ofthe wearable device 110 could extract an ECG waveform related to theelectrical activity of the wearer's 100 heart 101 during the secondperiod of time from voltage fluctuations between the first and second130 electrical contacts.

The wearer positioning skin of the finger (or some other location) ofthe second arm 105 b proximate to the second electrical contact 130could be performed a plurality of times to enable to extraction of ECGwaveforms during a plurality of respective periods of time. The wearerpositioning skin of the finger of the second arm 105 b proximate to thesecond electrical contact 130 could be performed at the initiative ofthe wearer, e.g., in response to the wearer having performed and/orbeing about to perform a strenuous task (e.g., exercise), experiencingsome symptoms (e.g., fatigue, nausea, vertigo, heart palpitations,orthostatic hypertension), having received and/or being about to receivea drug (e.g., having taken nitroglycerin). In some examples, the wearercould additionally operate the device to indicate some symptoms or otherinformation related to an extracted ECG waveform. Additionally oralternatively, the wearer positioning skin of the finger of the secondarm 105 b proximate to the second electrical contact 130 could beperformed in response to an indication (e.g., a vibration, a sound, avisual indication on a display of the device 100, an indication throughsome other device in communication with the wearable device 110) thatthe wearer should perform such an action to enable the extraction of anECG waveform by the wearable device 110.

FIG. 2 illustrates an electrical circuit 200 modeling elements of thewearer 100 and wearable device 110 of FIGS. 1A and 1B. The electricalcircuit 200 includes a time-varying voltage source 201 corresponding tothe time-varying electrical field generated by the heart 101 of thewearer 100. The electrical circuit 200 additionally includes elementscorresponding to the wearable device 110 (illustrated by bounding box210). These elements 210 include equivalent resistor/capacitor networks230, 240 corresponding to the electrical properties of the first andsecond 130 electrical contacts and their electrical coupling torespective first and second skin locations. The elements of the wearabledevice 210 additionally include a signal conditioner 220 electricallyconnected to the first 230 and second 240 electrical contacts andconfigured to extract an ECG waveform from voltage fluctuations betweenthe first 240 and second 240 electrical contacts. The electrical circuit200 further includes two resistors 205 a, 205 b representing theelectrical properties (e.g., resistance to current flow) of the arms 105a, 105 b and other tissue (e.g., chest tissue) between the heart 101 andthe first and second 130 electrical contacts. A switch 207 b representsthe control-able electrical contact between the second electricalcontact 130 and skin of the second arm 105 b. Thus, the switch 207 b isopen to model the electrical behavior of the wearer 100 and wearabledevice 110 during the first period of time (corresponding to thescenario illustrated by FIG. 1A) and open to model the electricalbehavior of the wearer 100 and wearable device 110 during the secondperiod of time (corresponding to the scenario illustrated by FIG. 1B).

Thus, an ECG waveform extracted when the wearer 100 positions skin ofthe finger (or some other location) of the second arm 105 b proximate tothe second electrical contact 130 could correspond to a lead I ECGrecording. That is, in embodiments wherein the wearable device 110 ismounted to a right wrist location and the signal conditioner extracts anECG waveform by sensing the voltage fluctuations of the first electricalcontact relative to the second electrical contact, the extracted ECGwaveform corresponds to a lead I ECG recording. Alternatively, thewearable device 110 could be mounted to a left wrist location, and theextracted ECG waveform could correspond to an inverted lead I ECGrecording. The user could indicate to the wearable device 110 (e.g.,using a user interface of the wearable device 110) that the wearabledevice is mounted to a left (or right) wrist location. Additionally oralternatively, the wearable device 110 could determine that it ismounted to a left (or right) wrist location based on features (e.g., thepolarity of the QRS complex) of an extracted ECG waveform.

Note that parameters of the electrical circuit 200 are related toelectrical properties of the body of the wearer 100, of the first andsecond 130 electrical contacts, and to properties of the interfacebetween the first and second 130 electrical contacts and respectivefirst and second skin locations. Thus, the parameters of the electricalcircuit 200 could be related to a dryness of other state of the skinlocations, a type of skin at the skin locations, a degree of forceapplied between the skin locations and respective electrical contacts,or other considerations. Further, the parameters of the electricalcircuit 200 could be related to the composition and configuration of theelectrical contacts (e.g., a composition of a surface of the electricalcontacts, a texture of the surface of the electrical contacts, ageometry of the electrical contacts). Correspondingly, one or moreproperties (e.g., an input impedance, a frequency response, a bandwidth,a sensitivity, a maximum input amplitude) of the signal conditioner 220could be specified and/or controlled relative to expected values ofthose properties of the body of the wearer 100, of the first and second130 electrical contacts, and/or of the interface between the first andsecond 130 electrical contacts and respective first and second skinlocations (e.g., to allow the extraction of low-noise, high-amplitude,or otherwise optimized ECG waveforms).

Electrical contacts of the wearable device 110 could be configured in avariety of ways to allow the extraction of an ECG waveform from voltagefluctuations between the electrical contacts under a range ofphysiological and environmental conditions. The electrical contactscould have a variety of surface compositions to allow ohmic (i.e.,related to conduction by ionic and/or redox reaction across the surfaceof the electrical contacts) and/or capacitive (i.e., related to theaccumulation of opposite charges on opposite sides of a surface of theelectrical contacts) electrical coupling between the electrodes and skinlocations of a wearer. Such surface compositions could include stainlesssteel, gold, platinum, silver, silver/silver-chloride, polymers orrubbers containing conductive particles, or other conductive orpartially conductive materials. Further, the shape and/or surfacetexture of the electrical contacts could be specified to control one ormore properties of the electrical interface of the electrical contactswith skin. For example, the electrical contacts could have a specifiedlarge area in contact with skin, could protrude from a housing towardthe skin (e.g., could have a rounded and/or pointed protrudinggeometry), could have a surface texture (e.g., to increase an effectivesurface area between a conductor of the electrical contact and fluids onthe surface of the skin), or could be configured in some other way.

In some examples, the electrical contacts could be configured to have asubstantially capacitive electrical contact with skin; that is, anelectrical contact could engage in substantially no direct ionic and/orredox conduction across the interface between the electrical contact andthe skin. Conduction of currents between such an electrode and the skincould instead consist substantially of the accumulation of oppositecharges on respective opposite sides of a substantially nonconductivebarrier between a conductor of the electrical contact and the skin. Forexample, an electrical contact could include a flat conductor having asubstantially nonconductive dielectric coating configured to be incontact with skin. Additionally or alternatively, an electrical contactcould have a textured conductive surface coated in a conformal layer ofsubstantially nonconductive material. Other compositions andconfigurations of electrodes are anticipated.

A signal conditioner or other electronics of the wearable device 110could include a variety of components configured in a variety of ways toallow one or more ECG waveforms to be extracted from voltagefluctuations between the first and second 130 electrical contacts whenthe first and second 130 electrical contacts are contacting appropriaterespective skin locations of the wearer 100 and/or to allow otheroperations and applications. The electronics could include analog and/ordigital electronic components to enable analog and/or digitalmanipulations of electrical signals related to voltage fluctuationsbetween the electrical contacts. Generally, the electronics includecomponents configured to amplify and filter voltage fluctuations betweenthe electrical contacts (e.g., one or more amplifiers, buffers, filters,operational amplifiers, resistors, capacitors, inductors, transistors,rectifiers, or some other linear or nonlinear electronic component orcombinations thereof).

For example, the electronics could be configured to generate anelectronic signal (e.g., to generate an extracted ECG waveform) that isrelated to a band-passed version of the voltage fluctuations between theelectrical contacts. This could include applying the voltagefluctuations to a band-pass filter having a pass-band betweenapproximately 0.05 Hertz and approximately 150 Hertz. Additionally oralternatively, an electronic signal could be digitally sampled and somedigital filtering could be performed (e.g., by a processor of thewearable device 110) to generate an extracted ECG waveform. Theelectronics could include fast recovery circuitry configured todetermine that one or more elements (e.g., amplifiers, filters) of theelectronics are saturated and to responsively control one or moreproperties of the electronics (e.g., operate an electronic switch todischarge a capacitor, change a corner frequency or other parameter of afilter) to reduce the electronic saturation of the one or more elementsof the electronics. Other configurations and applications of electronicsof the wearable device 110 are anticipated.

The wearable device 110 and uses thereof illustrated in FIGS. 1A and 1Bare illustrative examples; a wearable device as described herein couldbe configured in a variety of ways. Generally, such a wearable devicecould include at least one electrical contact disposed on or toward aninside surface of the wearable device (e.g., on an inside surface of ahousing, strap, or other element of the wearable device) such that theat least one electrical contact is in contact with a first external bodysurface at a first skin location to which the wearable device ismounted. Generally, such a wearable device could also include at leastone electrical contact disposed on or toward an outside surface (i.e.,an outside contact) of the wearable device (e.g., on an outside surfaceof a housing, strap, or other element of the wearable device) such thatthe at least one electrical contact is not in contact with an externalbody surface at the first skin location to which the wearable device ismounted. The wearable device could be further configured to preventelectrical contact between the outside contact and an external bodysurface at the first skin location to which the wearable device ismounted, e.g., by increasing a distance between the outside contact andthe external body surface, by disposing the outside contact on anoutside surface of the wearable device far from an edge of the outsidesurface, by providing a non-conductive barrier between the outsidecontact and the external body surface, or operating or configuring thewearable device in some other way.

A wearable device (e.g., 110) could include additional sensors. Forexample, the wearable device could include accelerometers, optical pulsesensors, photoplethysmographic sensors, pulse oximeters, thermometers,acoustical sensors, force sensors, electric field sensors, magneticfield sensors, or some other sensor(s) configured to detect one or moreproperties of a wearer of the wearable device and/or of the environmentof the wearable device. In some examples, information from differentsensors of the wearable device could be combined to determine one ormore properties of the wearer (e.g., to determine a health or medicalstate of the wearer).

For example, a wearable device could be configured to extract an ECGwaveform from voltage fluctuations between two or more skin locations ofa wearer. The wearable device could be further configured to detect avolume of blood in a portion of subsurface vasculature of the wearer ata plurality of points in time (e.g., by illuminating the portion ofsubsurface vasculature and detecting light responsively received formthe portion of subsurface vasculature, i.e., via photoplethysmography)to generate a waveform of the volume of blood in the portion ofsubsurface vasculature over time. Time differences or other comparisonsof features of the extracted ECG waveform and the determined volumewaveform (e.g., a time difference between a maximum of the volumewaveform and a corresponding QRS complex of the ECG waveform) could beused to determine a flow rate, a pressure wave speed and/or latency, orother information about the blood in the portion of subsurfacevasculature and/or information about the heart and vasculature of thewearer. Further, such determined information could be used to determinea health or medical state of the wearer, e.g., to determine a bloodpressure of the wearer, to determine a degree of atherosclerosis of thevasculature of the wearer, etc.

III. Example Wearable Devices

Wearable devices as described herein could be configured in a variety ofways. In some examples, a wearable device could be configured to bemounted to a wrist location of a first arm of the wearer. Further, sucha wearable device could include a first electrical contact disposed on ahousing (e.g., on an inside surface of the housing) of the wearabledevice and configured contact skin at wrist location when the wearabledevice is mounted on the wrist location. Such a wearable device couldadditionally include a second electrical contact (e.g., disposed on anoutside surface of the wearable device) configured to be contacted byskin of a second body surface on a second arm of the wearer such thatelectronics (e.g., a signal conditioner) of the wearable device couldextract an ECG waveform from voltage fluctuations between the first andsecond electrical contacts when the second electrical contact iscontacted by skin of the second body surface and the wearable device ismounted to the wrist location.

As an example, FIG. 3A illustrates a wearable device 300 a similar tothe wearable device 110 illustrated in FIGS. 1A and 1B. The wearabledevice 300 a can be configured to extract an ECG waveform from voltagefluctuations between skin at first and second external body surfaces.The term “wearable device,” as used in this disclosure, refers to anydevice that is capable of being worn at, on or in proximity to anexternal body surface, such as a wrist, ankle, waist, chest, or otherbody part. A mount 320 a, such as a belt, wristband, ankle band, etc.can be provided to mount the device at, on or in proximity to theexternal body surface. In some embodiments, a mount could additionallyor alternatively include an adhesive. For example, a mount could includean adhesive and could be configured such that it could be used to mounta wearable device to an external body surface of a wearer withoutwrapping around a part of the wearer (e.g., a limb). The mount 320 a mayprevent the wearable device 300 a from moving relative to the body toensure consistent contact between an electrical contact or other sensorof the wearable device 300 a and the skin to enable consistentextraction of an ECG waveform and/or measurement of some other propertyof the wearer. In one example, shown in FIG. 3, the mount 320 a takesthe form of a strap or band that can be worn around a part of the body.

A housing 310 a is disposed on the mount 320 a such that the housing 310a can be positioned on a first external surface of a first arm of thebody (e.g., a surface of a wrist of the body). The housing 310 a has anoutside surface 312 a that is away from the first external surface ofthe body and an inside surface (not shown) that is toward and/or incontact with the first external surface of the body when the housing 310a is positioned on the first external surface of the body. Similarly,the mount 320 a has an inside surface 324 a and an outside surface 322a. A second electrical contact 330 a is disposed in the middle of theoutside surface 312 a of the housing 310 a and configured to becontacted by skin of a second external body surface of a second arm ofthe body (i.e., an arm opposite an arm to which the wearable device 300a is mounted). Operated and/or mounted in this way, a first electricalcontact (not shown) disposed on the inside surface of the housing 310 acould contact skin at the first external surface of the body such thatan ECG waveform (as measured between the first and second external bodysurfaces, e.g., between a wrist of a first arm and a finger of a second,opposite, arm) could be extracted from voltage fluctuations between thefirst and second 330 a electrical contacts.

The first and second 330 a electrical contacts could be composed of anelectrically conductive material, such as a metal or a combination ofmetals, or a nonmetal conductor. The first and second 330 a electricalcontacts could be composed of the same material or different materials.The first and second 330 a electrical contacts could each be composed ofa single material or could be composed of multiple materials. Forexample, the electrical contacts could have a bulk composed of a firstmaterial and a surface plating of another material. For example, theelectrical contacts could have a bulk composed of copper and a surfacecomposed of gold or of gold alloyed with nickel and/or cobalt.Alternatively, the surface layer could be composed of stainless steel,gold, platinum, silver, silver/silver-chloride, polymers or rubberscontaining conductive particles, or other conductive or partiallyconductive materials. The surface layer could be deposited by a numberof methods familiar to one skilled in the art; for example,electroplating. Other compositions are possible, as well. Additionallyor alternatively, the electrical contacts could be configured to besubstantially capacitively coupled to respective external body surfacesby, e.g., including a flat conductor having a substantiallynonconductive dielectric coating configured to be in contact with skin.Other compositions and configurations of electrodes are anticipated.Further, protruding aspects of the electrical contacts could have aninscribed, cast, and/or pressed texture or pattern. Additionally oralternatively, the exposed aspects of the electrical contacts could beroughened mechanically, chemically, or by some other method.

One or both of the electrical contacts could be spring loaded. That is,the electrical contacts could be configured to include one or moresprings or other elements that could be reversibly compressed. The firstelectrical contact could be spring loaded in a direction perpendicularto an external surface of the body to which the housing 310 a could bemounted. That is, the first electrical contact could be spring loaded inorder to improve and/or make more consistent an electrical connectionbetween the first electrical contact and skin of the first external bodysurface to which the housing 330 a is mounted by the mount 320 a.Alternatively, the first and/or second 330 a electrical contacts couldbe fixed relative to housing 310 a.

The housing 310 a could be configured to be water-resistant and/orwater-proof. That is, the housing could be configured to includesealants, adhesives, gaskets, welds, press-fitted seams, and/or otherjoints such that the housing 310 a is resistant to water entering aninternal volume or volumes of the housing 310 a when the housing 310 ais exposed to water. The housing 310 a could further be water-proof,i.e., resistant to water entering an internal volume or volumes of thehousing 310 a when the housing 310 a is submerged in water. For example,the housing 310 a could be water-proof to a depth of 1 meter, i.e.,configured to resist water entering an internal volume or volumes of thehousing 310 a when the housing 310 a is submerged to a depth of 1 meter.Further, the interface between the housing 310 a and the first andsecond 330 a electrical contacts could be configured such that thecombination of the housing 310 a and the electrical contacts iswater-resistant and/or water-proof.

The wearable device 300 a includes electronics (not shown in FIG. 3)electronically coupled to the first and second 330 a electricalcontacts. The electronics (e.g., electronics configured as a signalconditioner or otherwise as described herein) are configured to extractan ECG waveform from voltage fluctuations between the first and second330 a electrical contacts when the first and second 330 a electricalcontacts are in contact with respective first and second externalsurfaces of the body.

The wearable device 300 a could be operated based an ECG waveformextracted as described herein. For example, the wearable device 300 acould be configured to determine a health or other state of a wearerbased on an extracted ECG waveform. Further, the wearable device 300 acould be configured to determine whether the wearable device 300 a ismounted to an external body surface of a wearer and/or that an ECGwaveform can be extracted using the first and second 330 a electricalcontacts based on a value, a change in value, and/or some other propertyof a current and/or voltage detected through and/or between the firstand second 330 a electrical contacts (e.g., a current and/or voltagedetected while a voltage and/or current is being applied, by electronicsof the wearable device 300 a, through and/or across the first and second330 a electrical contacts).

The electronics or other elements of the wearable device 300 a could beconfigured to prevent injury of a wearer and/or damage to the wearabledevice 300 a due to operation of the device to extract an ECG waveformfrom voltage fluctuations between two or more external body surfacesusing the first and second 330 a electrical contacts. Clamping diodesand/or associated blocking resistors could be included in the wearabledevice 300 a and configured to prevent voltages and/or currents above acertain specified maximum from being applied to the electrical contacts(and thus to the skin of the wearer) and/or to elements of the wearabledevice 300 a (e.g., components (e.g., an ADC) of a signal conditioner,components of a recharger coupled to the electrical contacts). Ablocking capacitor (i.e., a capacitor having a high specified value ofcapacitance) could be electrically disposed between one or more or theelectrical contacts and electronics of the wearable device 300 a toprevent the wearable device 300 a from injuring the skin of the externalbody surface(s) and/or causing electrochemical damage to the electricalcontacts (e.g., by preventing the application of direct current to theskin for a protracted period of time, by ensuring that current injectedinto the skin through the electrical contacts is essentially balanced).Other operations and configurations of the wearable device 300 a toprevent injury of a wearer and/or damage to the wearable device 300 aare anticipated.

The first and second 330 a electrical contacts, and any additionalelectrical contacts (not shown) protruding from and or disposed on thehousing 310 a could additionally be used for other purposes. Forexample, electronics disposed in the wearable device 300 a could be usedto sense a skin resistance, a skin capacitance, a body water content, abody fat content, a Galvanic skin potential (GSP), an electromyographic(EMG) signal, and/or some other physiological signal present at and/orthrough the electrical contacts. Additionally or alternatively, theelectrical contacts could be used to detect the presence of a chargingdevice or some other electronic system electrically connected to theelectrical contacts. The electronics could then use the electricalcontacts to receive electrical energy from the charging device or othersystem to recharge a rechargeable battery of the wearable device 300 aand/or to power the wearable device 300 a. Such a rechargeable batterycould additionally or alternatively be recharged wirelessly usingelectromagnetic energy received by a coil and other wireless chargingcircuitry disposed in the wearable device 300 a.

Alternatively, one or both of the electrical contacts of such a wearabledevice could be disposed on a band, strap, or other mount of the device.For example, FIG. 3B illustrates a wearable device 300 b that can beconfigured to extract an ECG waveform from voltage fluctuations betweenskin at first and second external body surfaces. A housing 310 b isdisposed on a mount 320 b such that the housing 310 b can be positionedon a first external surface of a first arm of the body (e.g., a surfaceof a wrist of the body). The housing 310 b has an outside surface 312 bthat is away from the first external surface of the body and an insidesurface (not shown) that is toward and/or in contact with the firstexternal surface of the body when the housing 310 b is positioned on thefirst external surface of the body. Similarly, the mount 320 b has aninside surface 324 b and an outside surface 322 b. A second electricalcontact 330 b is disposed on the outside surface 322 b of the mount 320b and configured to be contacted by skin of a second external bodysurface of a second arm of the body (i.e., an arm opposite an arm towhich the wearable device 300 b is mounted). Operated and/or mounted inthis way, a first electrical contact (not shown) disposed on the insidesurface of the housing 310 b could contact skin at the first externalsurface of the body such that an ECG waveform (as measured between thefirst and second external body surfaces, e.g., between a wrist of afirst arm and a finger of a second, opposite, arm) could be extractedfrom voltage fluctuations between the first and second 330 b electricalcontacts.

In some examples, such a wearable device could include a user interfaceconfigured to present and/or indicate information to a wearer and/or toreceive information (e.g., command inputs) from the wearer. For example,FIG. 3C illustrates a wearable device 300 c that can be configured toextract an ECG waveform from voltage fluctuations between skin at firstand second external body surfaces. A housing 310 c is disposed on amount 320 c such that the housing 310 c can be positioned on a firstexternal surface of a first arm of the body (e.g., a surface of a wristof the body). The housing 310 c has an outside surface 312 c that isaway from the first external surface of the body and an inside surface(not shown) that is toward and/or in contact with the first externalsurface of the body when the housing 310 c is positioned on the firstexternal surface of the body. A first electrical contact (not shown) isdisposed on the inside surface of the housing 310 c and a secondelectrical contact 330 c is disposed on the outside surface 312 c of thehousing 310 c. Further, the wearable device 300 c includes a userinterface 340 c disposed on the outer surface 312 c of the housing.

A wearer of the device 300 c may receive one or more recommendations oralerts generated from a remote server or other remote computing device,or from a processor within the device via the user interface 340 c. Thealerts could be any indication that can be noticed by the person wearingthe wearable device. For example, the alert could include a visualcomponent (e.g., textual or graphical information on a display), anauditory component (e.g., an alarm sound), and/or tactile component(e.g., a vibration). Further, the user interface 340 c may be configuredand/or operated to provide a visual display 342 c to provide anindication of a status of the device, a time, an extracted ECG waveform,or an indication of any other measured physiological parameters measuredby the device 300 c. Further, the user interface 340 c may include oneor more buttons and/or be configured as a touch screen for acceptinginputs from the wearer. For example, user interface 340 c may beconfigured to change the text or other visual information 342 c inresponse to the wearer touching one or more locations of the userinterface 340 c.

To allow for easier and/or more comfortable contact between anoutward-facing electrode (e.g., 330 a, 330 b, 330 c) and skin of anexternal body surface of a wearer (e g, skin of a finger, hand, or otherpart of a wearer's body) and/or according to some other application, thesize, shape, number, and/or disposition of such outward-facingelectrode(s) could be different than shown above. For example, anoutward-facing electrode could partially or completely encircle a bandor strap of a wearable device, cover a larger area of an outside surfaceof a housing (e.g., completely cover such an outside surface), or beconfigured and/or disposed in some other way. For example, such anoutward facing electrode could completely or partially encircle an outeredge of an outside surface of a housing of a wearable device and/orcompletely or partially encircle a display or other user interfaceelement disposed on such an outside surface. For example, FIG. 3Dillustrates a wearable device 300 d that can be configured to extract anECG waveform from voltage fluctuations between skin at first and secondexternal body surfaces. A housing 310 d is disposed on a mount 320 dsuch that the housing 310 d can be positioned on a first externalsurface of a first arm of the body (e.g., a surface of a wrist of thebody). The housing 310 d has an outside surface 312 d that is away fromthe first external surface of the body and an inside surface (not shown)that is toward and/or in contact with the first external surface of thebody when the housing 310 d is positioned on the first external surfaceof the body. A first electrical contact (not shown) is disposed on theinside surface of the housing 310 d. A user interface 340 d is disposedon the outside surface 312 d of the housing 310 d A second electricalcontact 330 d is disposed along an edge of the outside surface 312 d ofthe housing 310 d completely enclosing the user interface 340 d.

Other configurations of a wearable device configured to extract an EGwaveform from two or more skin locations of the body of a wearer areanticipated. Such wearable devices could include more than twoelectrodes configured to provide additional information to extractadditional ECG waveforms, to extract higher-quality (e.g.,higher-magnitude, higher signal-to-noise-ratio) ECG waveforms, to detectsome other information (e.g., to detect a skin resistance, to detect aGalvanic skin response, to detect an EMG signal (e.g., an EMG signalfrom muscles in a wrist of a wearer), or to enable some otherapplication. In some examples, an electrical contact could additionallybe configured to detect contact with skin (e.g., a finger) of the wearerand the wearable device could operate responsive to such a detection,e.g., to extract an ECG waveform from voltage fluctuations between theelectrical contact and some other electrical contact(s). Additionally oralternatively, touch detection by an electrical contact could be used toreceive an input from the wearer, e.g., to act as a ‘button press’ orother indication of a wearer's intent. Further, a wearable device couldinclude multiple such electrical contacts configured to detect skincontact (e.g., to initiate an ECG waveform extraction, to determine userinput) and to enable ECG waveform extraction. Additionally oralternatively, such an electrode could form a transparent orsemi-transparent layer disposed on a display of the wearable device. Forexample, a layer of indium-tin-oxide, an array of fine wires or otherconductive elements, or some other elements could be disposed on adisplay and configured to act as an electrical contact. Additionally oralternatively, an electrode of a touchscreen could be configured tocapacitively couple with voltage fluctuations of a skin location of awearer such that an ECG waveform could be extracted from voltagefluctuations between the touchscreen electrode and some other electricalcontact(s) of the wearable device.

In some examples, the wearable device (e.g., a housing 310 a, 310 b, 310c, 310 d of the wearable device 300 a, 300 b, 300 c, 300 d) furtherincludes at least one detector for detecting at least one otherphysiological parameter, which could include any parameters that mayrelate to the health of the person wearing the wearable device and/orthe environment of the wearable device. For example, the detector couldbe configured to measure acceleration of the wearable device, a magneticfield, an electric field, an ambient light, a respiration rate, a skintemperature, etc. At least one of the detectors could be configured tonon-invasively measure a volume of blood circulating in subsurfacevasculature proximate to the wearable device. In a non-exhaustive list,the detector may include any one of an optical (e.g., CMOS, CCD,photodiode), acoustic (e.g., piezoelectric, piezoceramic),electrochemical (voltage, impedance), thermal, mechanical (e.g.,pressure, strain, acceleration, rotation), magnetic, or electromagnetic(e.g., RF, magnetic resonance) sensor.

For example, a wearable device could be configured to extract an ECGwaveform from voltage fluctuations between two or more skin locations ofa wearer. The wearable device could be further configured to detect avolume of blood in a portion of subsurface vasculature of the wearer ata plurality of points in time (e.g., by illuminating the portion ofsubsurface vasculature and detecting light responsively received formthe portion of subsurface vasculature, i.e., via photoplethysmography)to generate a waveform of the volume of blood in the portion ofsubsurface vasculature over time (e.g., a photoplethysmographic signal).Time differences or other comparisons of features of the extracted ECGwaveform and the determined volume waveform (e.g., a time differencebetween a maximum of the volume waveform and a corresponding QRS complexof the ECG waveform) could be used to determine a flow rate, a pressurewave speed and/or latency, or other information about the blood in theportion of subsurface vasculature and/or information about the heart andvasculature of the wearer. Further, such determined information could beused to determine a health or medical state of the wearer, e.g., todetermine a blood pressure of the wearer, to determine a degree ofatherosclerosis of the vasculature of the wearer, etc.

Further, a wearable device as described herein could be modular. Thatis, one or more components of such a wearable device could bereplaceable, extensible, and/or otherwise reconfigurable to add and/orremove capabilities of the wearable device. For example, a wearabledevice could include a housing containing a battery, a communicationsinterface, a touchscreen user interface, and general-purpose electronicsto enable a variety of applications of a wearable device. The wearabledevice could further include a modular mount configured to mount thehousing to an external body surface and to enable some applications ofthe wearable device, e.g., by including one or more sensors. Forexample, a first modular mount could be configured to mount the housingaround a wrist of a wearer and to enable extraction of an ECG waveformfrom voltage fluctuations between the arms of a wearer by providing asecond electrical contact on an outside surface of the mount (e.g., anouter surface of a frame encircling the housing) to complement a firstelectrical contact provided by the housing on an inside surface of thehousing. A second modular mount could be configured to mount the housingaround the chest of a wearer and to enable detection of breathingpatterns of the wearer by providing a strain sensor in a band of themount that encircles the chest of the wearer.

FIG. 4A illustrates a top perspective view of an example wearable device400 including a central housing 410 configured to be removably seated ina frame 450 of a modular mount. The modular mount additionally includesa band (not shown) connected to the frame 450 and configured to mountthe central housing 410 to an external body surface (e.g., a wrist) of awearer. The central housing 410 includes a user interface 420 disposedon an outer surface of the central housing 410 (e.g., a surface oppositethe external body surface when the central housing 410 is mounted to theexternal body surface by the modular mount). The user interface 420 is atouchscreen interface, configured to present visual indications to awearer (e.g., by spatially modulating an emitted light of the userinterface 420 and/or by spatially modulating a reflectivity of the userinterface 420). The frame 450 includes a nonconductive inner portion 470and a conductive outer portion 460. The outer portion 460 is configuredto act as an electrical contact and to contact skin of an external bodysurface of the wearer (e.g., skin of a finger of the wearer). The outerportion 460 encircles the user interface 420 when the central housing410 is seated in the frame 450 (as shown in FIG. 4A). The inner portion470 of the frame 450 includes mounting points 475 configured to attach aband, strap, or other means of securing the wearable device 400 to anexternal body surface (e.g., the mounting points 475 could be configuredto attach to a standard watch band, i.e., they could be approximately 26millimeters apart, 20 millimeters apart, or some other distance apartaccording to a stand watch band size).

FIG. 4B illustrates a bottom perspective view of the wearable device 400illustrating elements disposed on an inside surface of the centralhousing 410 (i.e., elements disposed toward the external body surfacewhen the central housing 410 is mounted to the external body surface bythe modular mount). Electrical contacts 430 a, 430 b are disposed on theinside surface of the central housing 410. The electrical contacts 430a, 430 b could be configured to enable a variety of applications of thewearable device 400. For example, the electrical contacts 430 a, 430 bcould be operated to detect a skin resistance, a skin capacitance, aGalvanic skin response, a body water content, a body fat content, orother information by passing a current through and/or applying a voltageto skin proximate to the wearable device and detecting a correspondingvoltage across and/or current through the electrical contacts 430 a, 430b. Further, a Galvanic skin voltage, an EMG waveform, or some otherelectrophysiological voltage signal could be detected through theelectrical contacts 430 a, 430 b. In some examples, an electro-hapticstimulus could be delivered to a wearer though the electrical contacts430 a, 430 b. In some examples, a temperature sensor could be thermallycoupled to one or more of the electrical contacts 430 a, 430 b to enablethe detection of the temperature of skin proximate to the one or moreelectrical contacts 430 a, 430 b.

Further, an ECG waveform could be extracted from voltage fluctuationsbetween the outer portion 460 of the frame and one or more electricalcontacts 430 a, 430 b when the central housing 410 is mounted to a firstexternal body surface (e.g., skin of a wrist of a first arm of a wearer)and a second body surface (e.g., skin of a finger of an arm of thewearer opposite the arm to which the wearable device is mounted) is incontact with the outer portion 460 of the frame 450. Other operation ofthe wearable device 400 to extract and ECG signal of a wearer, asdescribed herein or otherwise, are anticipated.

In some examples, the outer portion 460 of the frame and one or moreelectrical contacts 430 a, 430 b could be composed of similar materialsand/or configured to couple to voltage fluctuations of skin similarly.For example, the outer portion 460 of the frame and one or moreelectrical contacts 430 a, 430 b could all have surfaces composed ofsilver/silver-chloride and could make ohmic electrical contact withskin. In another example, the outer portion 460 of the frame and one ormore electrical contacts 430 a, 430 b could all have surfaces composedof a substantially non-conductive dielectric and could makesubstantially capacitive electrical contact with skin. Further, theouter portion 460 of the frame and one or more electrical contacts 430a, 430 b could be composed of different materials and/or configured tocouple to voltage fluctuations of skin differently. For example, theouter portion 460 of the frame could have surfaces composed ofsilver/silver-chloride and could make ohmic electrical contact withskin, while the electrical contacts 430 a, 430 b could have surfacescomposed of a substantially non-conductive dielectric and could makesubstantially capacitive electrical contact with skin. Othercombinations of electrode configurations and compositions areanticipated.

The central housing 410 additionally includes an optical sensor 440. Theoptical sensor 440 includes a photodetector 441 and four light sources443 a, 443 b, 443 c, 443 d. The photodetector 441 and light sources 443a, 443 b, 443 c, 443 d are disposed behind protective windows 445. Thefour light sources 443 a, 443 b, 443 c, 443 d could be similarly ordifferently configured. The photodetector could be any elementconfigured to electronically detect one or more properties (e.g.,wavelength, spectral profile, amplitude, amplitude within a specifiedrange of wavelengths) of received light (e.g., a photodiode, aphototransistor, a photoresistor, an avalanche photodiode). The fourlight sources 443 a, 443 b, 443 c, 443 d could include LEDs, laser, orother elements configured to emit light. Further, the four light sources443 a, 443 b, 443 c, 443 d could be configured to emit light having oneor more specified properties (e.g., a specified wavelength, a specifiedamplitude, a specified waveform over time, a specified pulse or othertiming). The optical sensor 440 could be configured to illuminate targettissues (e.g., using the light sources 443 a, 443 b, 443 c, 443 d) andto detect light responsively or otherwise emitted from the target tissue(e.g., using the photodetector 441) to detect one or more properties ofthe target tissue.

FIG. 4C illustrates a bottom perspective view of the wearable device 400when the central housing 410 has been unseated from the frame 450. FIG.4C illustrates a nonconductive housing 415, a wired interface 419, andcontact pads 417 of the central housing. The wired interface 419 couldbe any interface configured to receive one or more conductorsconfigured, e.g., as a connector such that power and electronic signalsmay be transmitted to and/or received from electronics disposed in thecentral housing 410. For example, the wired interface 419 could be amicro-USB interface. The contact pads 417 are configured to allowelectrical contacts between electronics of the central housing 410 andelectronics or other elements of a modular frame (e.g., the conductiveelectrical contact formed by the outer portion 460 of the frame 450).These elements are further illustrated by FIG. 4D, which illustrates atop perspective view of the central housing 410.

Note that the contact pads 417 could be electrically connected withinthe central housing 410 or could be electrically independent. That is,the contact pads 417 could be electrically connected together such thatthe contact pads 417 cannot be used to transfer different electricalsignals. Alternatively, the contact pads 417 could be electricallydistinct (e.g., could be connected to separate components of electronicswithin the central housing 410) and thus could be used to transferdifferent electrical signals. For example, the four contact pads 417could be connected to respective four distinct electrical contacts orelectrodes of a modular frame into which the central housing 410 couldbe removably seated. Additionally or alternatively, a modular framecould electrically connect one or more of the four contact pads 417together according to some application. For example, a first contact padcould be configured to detect a voltage, a second contact pad could beconfigured to source and/or sink a specified current, and the modularframe could connect the first and second contact pads to a singleelectrical contact to enable the determination of a resistance of sometarget (e.g., of a portion of skin, by determining a voltage across theportion of skin related to the specified current injected into theportion of skin) In some applications, two of the contact pads 417 couldbe configured to provide power to a component of the modular mount, andthe remaining two contact pads 417 could be configured to transmitand/or received data to/from elements of the modular mount (e.g., anactive sensor of the modular mount). Additionally or alternatively, sucha configuration of the contact pads 417 could be used to facilitatecommunication between the central housing 410 and some other system,e.g., to facilitate reprogramming of electronics of the central housing410, to facilitate data transfer of logged data stored in a data storageof the central housing, or some other application. Additional oralternative configurations and applications of the contact pads 417 andof the central housing 410 are anticipated.

FIGS. 4E and 4F show bottom perspective and top perspective explodedviews of the frame 450, respectively. The frame 450 includes fourspring-loaded contacts 455 configured to maintain electrical contactbetween the outer portion 460 of the frame 450 and the contact pads 417of the central housing 410 when the central housing 410 is seated in theframe 450. The spring-loaded contacts 455 are disposed within andretained by respective holes 475 formed in the inner portion 470 of theframe 450. Note that some or all of the spring-loaded contacts 455 couldalternatively be disposed as part of the central housing 410. Furtherall of the spring-loaded contacts 455 are in electrical contact witheach other and with the outer portion 460 (i.e., the electrical contact)of the frame 450, but individual contacts of the spring-loaded contacts455 could be in electrical contact with electrically distinct elements(e.g., separate electrical contacts, some other electrical and/orelectronic element(s)) of a modular frame.

FIG. 5 is a simplified schematic of a system 500 including one or morewearable devices 510. The one or more wearable devices 510 may beconfigured to transmit data via a communication interface 515 over oneor more communication networks 520 to a remote server 530. In oneembodiment, the communication interface 515 includes a wirelesstransceiver for sending and receiving communications (e.g., indicationsof a measured skin resistance and/or capacitance) to and from the server530. In further embodiments, the communication interface 515 may includeany means for the transfer of data, including both wired and wirelesscommunications. For example, the communication interface 515 may includea universal serial bus (USB) interface or a secure digital (SD) cardinterface. Communication networks 520 may include any of: a plain oldtelephone service (POTS) network, a cellular network, a fiber networkand a data network. The server 530 may include any type of remotecomputing device or remote cloud computing network. Further,communication network 520 may include one or more intermediaries,including, for example wherein the wearable device 510 transmits data toa mobile phone or other personal computing device, which in turntransmits the data to the server 530.

In addition to receiving communications from the wearable device 510,such as data regarding health and/or affect state as input by the useror extracted electrocardiographic (ECG) waveforms, the server may alsobe configured to gather and/or receive either from the wearable device510 or from some other source, information regarding a wearer's overallmedical history, environmental factors and geographical data. Forexample, a user account may be established on the server for everywearer that contains the wearer's medical history. Moreover, in someexamples, the server 530 may be configured to regularly receiveinformation from sources of environmental data, such as viral illness orfood poisoning outbreak data from the Centers for Disease Control (CDC)and weather, pollution and allergen data from the National WeatherService. Further, the server may be configured to receive data regardinga wearer's health state from a hospital or physician. Such informationmay be used in the server's decision-making process, such as recognizingcorrelations and in generating clinical protocols.

Additionally, the server may be configured to gather and/or receive thedate, time of day and geographical location of each wearer of the deviceduring each measurement period. If measuring physiological parameters ofthe user (e.g., extracted ECG waveforms), such information may be usedto detect and monitor spatial and temporal spreading of diseases. Assuch, the wearable device may be configured to determine and/or providean indication of its own location. For example, a wearable device mayinclude a GPS system so that it can include GPS location information(e.g., GPS coordinates) in a communication to the server. As anotherexample, a wearable device may use a technique that involvestriangulation (e.g., between base stations in a cellular network) todetermine its location. Other location-determination techniques are alsopossible.

Further, some embodiments of the system may include privacy controlswhich may be automatically implemented or controlled by the wearer ofthe device. For example, where a wearer's collected data are uploaded toa cloud computing network for analysis by a clinician, the data may betreated in one or more ways before it is stored or used, so thatpersonally identifiable information is removed. For example, a user'sidentity may be treated so that no personally identifiable informationcan be determined for the user, or a user's geographic location may begeneralized where location information is obtained (such as to a city,ZIP code, or state level), so that a particular location of a usercannot be determined.

Additionally or alternatively, wearers of a device may be provided withan opportunity to control whether or how the device collects informationabout the wearer (e.g., information about a user's medical history,social actions or activities, profession, a user's preferences, or auser's current location), or to control how such information may beused. Thus, the wearer may have control over how information iscollected about him or her and used by a clinician or physician or otheruser of the data. For example, a wearer may elect that data, such ashealth state and physiological parameters, collected from his or herdevice may only be used for generating an individual baseline andrecommendations in response to collection and comparison of his or herown data and may not be used in generating a population baseline or foruse in population correlation studies.

IV. Example Electronics Disposed in a Wearable Device

FIG. 6 is a simplified block diagram illustrating the components of awearable device 600, according to an example embodiment. Wearable device600 may take the form of or be similar to one of wearable device 110,210, 300 a, 300 b, 300 c, 300 d, and 400 shown in FIGS. 1A-B, 2, 3A-D,and 4A-4F. However, wearable device 600 may also take other forms, forexample, an ankle, waist, or chest-mounted device.

In particular, FIG. 6 shows an example of a wearable device 610 having asignal conditioner 330 for extracting an electrocardiographic (ECG)waveform from voltage fluctuations between two skin locations proximateto the wearable device 610, a rechargeable battery 635, a user interface680, communication interface 690 for transmitting data to a server, atemperature sensor 644, and processor(s) 650. The components of thewearable device 600 may be disposed on or within a mount and/or housingfor mounting the wearable device and components thereof to an externalbody surface, e.g., one of the two skin locations from which the signalconditioner 330 is configured to extract an ECG waveform. The wearabledevice 610 also includes a first electrical contact 640 and a secondelectrical contact 645 operatively coupled to the signal conditioner630. The signal conditioner 630 uses the first and second electricalcontacts 640, 645 to extract an ECG waveform from voltage fluctuationsbetween first and second skin locations proximate to respective firstand second electrical contacts 640, 645. The signal conditioner 630could be configured to perform other functions using the first andsecond electrical contacts 640, 645 and/or further electrical contactsof the wearable device 600. For example, the signal conditioner 630could be configured to interface with a charger or other external deviceor system to power the electronics and to recharge the rechargeablebattery 635, to determine that the first and second electrical contacts640, 645 are in contact with skin and/or that an ECG waveform can beextracted from voltage fluctuations between them 640, 645, to determinea skin resistance and/or capacitance between the electrical contacts640, 645 and/or some other electrical contacts, or some other function(s). Additionally or alternatively, the rechargeable battery 635 couldbe charged wirelessly using a coil and/or other components of thewearable device 600 (not shown). Additionally, the temperature sensor644 is thermally coupled to the first electrical contact 640 such thatthe temperature sensor 644 can be used to obtain a measurement relatedto the temperature of skin proximate to the first electrical contact640.

Processor 650 may be a general-purpose processor or a special purposeprocessor (e.g., digital signal processors, application specificintegrated circuits, etc.). The one or more processors 650 can beconfigured to execute computer-readable program instructions 672 thatare stored in a computer readable medium 660 (i.e., data storage) andare executable to provide the functionality of a wearable device 600described herein.

The computer readable medium 660 may include or take the form of one ormore non-transitory, computer-readable data storage media that can beread or accessed by at least one processor 650. The one or morecomputer-readable storage media can include volatile and/or non-volatilestorage components, such as optical, magnetic, organic or other memoryor disc storage, which can be integrated in whole or in part with atleast one of the one or more processors 650. In some embodiments, thecomputer readable medium 660 can be implemented using a single physicaldevice (e.g., one optical, magnetic, organic or other memory or discstorage unit), while in other embodiments, the computer readable medium660 can be implemented using two or more physical devices.

The signal conditioner 630 could include a variety of componentsconfigured in a variety of ways to allow one or more ECG waveforms to beextracted from voltage fluctuations between the electrical contacts 640,645 when the electrical contacts 640, 645 are contacting appropriaterespective skin locations of a wearer and/or to allow other operationsand applications. The signal conditioner 630 could include analog and/ordigital electronic components to enable analog and/or digitalmanipulations of electrical signals related to voltage fluctuationsbetween the electrical contacts 640, 645. In some examples, the signalconditioner 630 could include one or more analog electronic components(e.g., amplifiers, transistors, op-amps, analog filters) assembled intoan analog front-end and configured to amplify, buffer, filter, orotherwise act on voltage fluctuations between the electrical contacts640, 645 and to present one or more analog electronic outputs to digitalcomponents of the signal conditioner 630 and/or other elements of thewearable device 600 (e.g., to an ADC or other component of the processor650).

Generally, the signal conditioner 630 includes components configured toamplify and filter voltage fluctuations between the electrical contacts640, 645. The signal conditioner 630 could include one or moreamplifiers, buffers, filters, operational amplifiers, resistors,capacitors, inductors, transistors, rectifiers, or some other linear ornonlinear electronic component or combinations thereof. Such componentscould be formed as a number of discrete signal processing blocks (e.g.,discrete sets of components configured to perform some operation(s) onelectronic input(s) to form electronic output(s)) that are connectedtogether (e.g., the output(s) of a first block form the input(s) of oneor more other blocks).

In some embodiments, the signal conditioner 630 could be configured togenerate an electronic signal (e.g., to generate an extracted ECGwaveform) that is related to a band-passed version of the voltagefluctuations between the electrical contacts 640, 645. This couldinclude applying the voltage fluctuations to a band-pass filter having apass-band between approximately 0.05 Hertz and approximately 150 Hertz.The signal conditioner 630 could additionally apply a notch filter (at,e.g., approximately 60 Hertz) to remove some narrow-band signal from thevoltage fluctuations (e.g., to remove approximately 60 Hertz noiseemitted by power mains in the environment of the wearable device 600).Additionally or alternatively, an electronic signal could be digitallysampled and some digital filtering could be performed (e.g., by theprocessor 650) to generate an extracted ECG waveform. In such examples,the processor 650 and elements thereof (e.g., an ADC of the processor)could be considered part of an overall signal conditioner configured toextract an ECG waveform from voltage fluctuations between the electricalcontacts 640, 645.

The signal conditioner 630 could include a fast response circuit orother circuitry or components configured to allow the signal conditioner630 to extract an ECG waveform after the voltage fluctuations betweenthe electrical contacts 640, 645 exhibit a large change (e.g., a changein baseline voltage level, a spike or other transient related to anelectrostatic discharge, a skin location coming into contact with one ofthe electrical contacts, and/or a skin location moving relative to oneor both of the electrical contacts 640, 645). For example, the signalconditioner 630 could be configured to determine that one or moreelements (e.g., amplifiers, op-amps, signal processing blocks) of thesignal conditioner 630 are electronically saturated (i.e., outputting amaximal and/or minimal signal level, or having an internal signal thathas a maximal or minimal value) and to responsively control one or moreproperties of the signal conditioner 630 to reduce the electronicsaturation of the one or more elements of the signal conditioner 630.

Determining that one or more elements of the signal conditioner areelectronically saturated could include sampling an output or otherelectronic signal of the signal conditioner 630 using an ADC and makinga determination related to one or more digital outputs of the ADC,applying an output or other electronic signal of the signal conditioner630 to a comparator, Schmitt trigger, or other digital component, orsome other determination. Further, controlling one or more properties ofthe signal conditioner 630 to reduce the electronic saturation of theone or more elements of the signal conditioner 630 could includedischarging a capacitor, switching in and/or out one or moresignal-processing blocks of the signal conditioner 630, and/or changinga corner frequency, pass-band, or other parameter(s) of a filter (e.g.,increasing a corner frequency of a high-pass filter to allow the outputof the filter to more quickly reduce from a saturation level). Thesemethods of control could be implemented by operating one or moreelectronic switches, transistors, or other elements.

Additionally or alternatively, fast response or other circuitry of thesignal conditioner 630 could prevent electronic saturation of one ormore elements of the signal conditioner 630 by having a nonlinearproperty; for example, a metal-oxide varistor or other electronicelements or combinations thereof having a nonlinear current-voltagecharacteristic (e.g., having a lower resistance and/or impedance athigher voltages than at lower voltages) could be included in the signalconditioner 630 (e.g., could be connected across a filtering or othercapacitor, could be connected between a signal line and a ground plane).Fast response or other circuitry of the signal conditioner 630configured to prevent electronic saturation of one or more elements ofthe signal conditioner 630 could exhibit hysteresis. For example, fastresponse circuitry could include a Schmitt trigger configured to close acapacitor-discharging switch when the voltage across the capacitorexceeds a first specified level and to subsequently open thecapacitor-discharging switch when the voltage across the capacitor fallsbelow a second specified level.

The signal conditioner 630 could include circuitry or other elementsconfigured to detect and/or determine whether the first and secondelectrical contacts 640, 645 are in contact with skin and/or that an ECGwaveform can be extracted from voltage fluctuations between them 640,645. The signal conditioner 630 could include circuitry (e.g., voltagedividers, relaxation oscillators, current injectors) configured toactively or passively detect an effective resistance and/or capacitancebetween the first and second electrical contacts 640, 645 that could beused to determine that the first and second electrical contacts 640, 645are in contact with skin and/or that an ECG waveform can be extractedtherefrom. Such circuitry could additionally be configured and/oroperated to detect other properties of a wearer, e.g., a body watercontent, a body fat content. Additionally or alternatively, the signalconditioner 630 could include circuitry (e.g., comparators, Schmitttriggers, overvoltage sensors, differentiators, fast response circuitry)configured to detect electrostatic discharges, voltage transients,changes in voltage offsets, or other properties of voltage fluctuationsbetween the first and second electrical contacts 640, 645 that arerelated to the electrical contacts 640, 645 coming into and/or leavingcontact with skin of a wearer.

A voltage sensor of the signal conditioner 630 (and/or of the processor650) could include one or more comparators, Schmitt triggers,direct-conversion ADCs, successive-approximation ADCs, sigma-delta ADCs,or some other type(s) of ADC. The voltage sensor could include anamplifier, a filter, a sample-and-hold, and/or some other components.Further, individual elements of the signal conditioner 630 could beembodied as respective discrete components. Additionally oralternatively, one or more elements of the signal conditioner 630 couldbe incorporated into one or more integrated circuits (e.g., anintegrated circuit that includes elements of the processor 650, thecommunication interface(s) 690, and/or elements of the wearable device600. In examples where the signal conditioner 630 are included in awearable device composed of multiple housings or other subassemblies,the elements of the signal conditioner 630 could all be disposed in asingle housing or subassembly or elements of the signal conditioner 630could be disposed in multiple housings or subassemblies and connectedusing wires, cables, or other means passing between housings orsubassemblies.

In some examples, voltage sources, electronic switches, amplifiers,filters, op-amps, voltage sensors (e.g., ADCs, comparators, Schmitttriggers), and/or other elements of the signal conditioner 630 could beelements of a microprocessor (e.g., of 650) that are electronicallycoupled to a pin of the microprocessor (e.g., logic gates, capacitors,high-impedance electrical switches (e.g., CMOS FETs), or othermicroelectronics). For example, a voltage source of the signalconditioner 630 could be an internal voltage supply of themicroprocessor, and a voltage source switch of the signal conditioner630 could be a gate of the microprocessor configured to electricallyconnect the internal voltage supply and/or an internal ground of themicroprocessor to a pin of the microprocessor and to appear as a highimpedance element when not connecting the pin to the internal voltagesupply and/or the internal ground (e.g., to provide a ‘three-state’digital output to the pin). An ADC of the microprocessor couldadditionally be configured to electrically connect to the pin and to actas a voltage sensor of the signal conditioner 630.

In some examples, the signal conditioner 630 could include circuitry toprotect elements of the wearable device 600 (e.g., to protectamplifiers, filters, voltage sensors, or other elements of the signalconditioner 630) from high voltages and/or currents present acrossand/or through the electrical contacts 640, 645. For example, the signalconditioner 630 could include clamping diodes, blocking resistors,blocking capacitors, electronic switches, or other elements configuredto prevent components of the signal conditioner 630 from being damagedby voltages and/or currents at/through the electrical contacts 640, 645.These elements of the signal conditioner 630 could be configured toprotect the wearable device 600 from electrostatic discharges from theenvironment of the wearable device 600.

The signal conditioner 630 could include additional components. In someexamples, the signal conditioner 630 could include a rechargerconfigured to recharge the rechargeable battery 635 and to be poweredthrough the electrical contacts 640, 645 and/or some additionalelectrical contact(s). In some examples, the wearable device 600 couldbe configured to be mounted on an external charger. The external chargercould be configured to apply a voltage and/or current to the electricalcontacts (e.g., 640, 645) sufficient to power the recharger to rechargethe rechargeable battery 635. The signal conditioner 630 could includerectifiers, capacitors, or other elements disposed electrically betweenthe recharger and the electrical contacts (e.g., 640, 645). Therectifiers or other elements could be configured to reduce electricalinterference in ECG waveform measurements made using the electricalcontacts 640, 645 when the wearable device 600 is mounted to an externalsurface of a wearer and not mounted to an external charger. Additionallyor alternatively, the wearable device 600 could include a coil and othercomponents configured to receive electromagnetic energy (e.g., from awireless charger) and to recharge the rechargeable battery 635 using thereceived electromagnetic energy. The signal conditioner 630 couldinclude components configured to detect an EMG, a skin resistance, askin capacitance, a body water content, a body fat content, a Galvanicskin response, or some other electrical signal using the electricalcontacts 640, 645 and/or some additional electrical contact(s). Thesignal conditioner 630 could include components to operate some othersensors (e.g., accelerometers, optical pulse sensors,photoplethysmographic sensors, pulse oximeters, thermometers, thetemperature sensor 644) configured to detect one or more properties of awearer of the wearable device 600 and/or of the environment of thewearable device 600.

Note that, while the signal conditioner 630, processor(s) 650,rechargeable battery 635, and other components are sometimes describedherein as being disposed on or within a single housing, otherconfigurations are anticipated. In some examples, a wearable devicecould include multiple housings, and the components of the wearabledevice 600 could be distributed amongst the multiple housings. Forexample, a first housing could contain some elements of the signalconditioner 630 (for example, ECG waveform extraction electronics,temperature sensing electronics) and the electrical contacts 640, 645could protrude from the first housing. A second housing could includethe recharger electronics and the rechargeable battery 635 and elementsdisposed in the second housing could be electrically connected toelements disposed in the first housing. In some examples, the wearabledevice 600 could include a modular mount and a housing configured to beremovably seated in a frame of the modular mount. The first electricalcontact 640, elements of the signal conditioner 630, and/or otherelements of the wearable device 600 (e.g., 650, 660, 680, 690, 635)could be disposed on or within the housing. The second electricalcontact 645 (and other elements) could be disposed on or within themodular mount (e.g., on an outside surface of the frame, on an outsidesurface of a band of the modular mount) and maintained in electricalcontact with elements of the housing (e.g., 630) via spring-loadedcontact(s) or some other means. Other numbers of housings,configurations of housings, and dispositions of components withinmultiple housings are anticipated.

The program instructions 672 stored on the computer readable medium 660may include instructions to perform or facilitate some or all of thedevice functionality described herein. For instance, programinstructions 672 could include instructions to operate the signalconditioner 630 to extract an ECG waveform from voltage fluctuationsbetween the electrical contacts 640, 645. The program instructions 672could additionally include instructions to operate other elements of thesignal conditioner 630 (e.g., switches, circuit breakers, FETs) toprotect other elements of the wearable device 600 that are electricallycoupled to the electrical contacts 640, 645 (e.g., an amplifier and/orvoltage sensor of the signal conditioner 630) from being damaged. Theprogram instructions 672 could include instructions to operate based onparameter and user data 674 stored in the computer readable medium 660and/or modify the parameters and user data 674. For example, theparameters and user data 674 could include calibration data for thewearable device 600 and/or stored ECG waveforms (and/or featuresthereof, e.g., Q-T intervals, QRS complex parameters) extracted usingthe wearable device 600.

The program instructions 672 stored on the computer readable medium 660could include instructions for operating the signal conditioner 630 toextract an ECG waveform from voltage fluctuations between the electricalcontacts 640, 645. The instructions could include instructions toactivate and/or set a value of a current source, a voltage source, aprogrammable resistor, an ADC, one or more electronic switches, and/orsome other component(s) of the signal conditioner 630. The instructionscould include instructions to set a gain, bandwidth, corner frequency,notch frequency, or other property of an amplifier and/or filter of thesignal conditioner 630. The instructions could include instructions tooperate a voltage or current sensor to make one or more measurementsrelating to the voltage between the electrical contacts 640, 645. Theinstructions could include instructions to operate a voltage or currentsensor to make a series of measurements during a respective series ofregularly spaced periods of time relating to the voltage between theelectrical contacts 640, 645.

The instructions could include instructions to determine whether thefirst and second electrical contacts 640, 645 are in contact with skinand/or that an ECG waveform can be extracted from voltage fluctuationsbetween electrical contacts 640, 645 and to responsively extract an ECGwaveform. This could include analyzing voltage fluctuations between theelectrical contacts 640, 645 to determine whether the voltagefluctuations contain ECG waveforms. Additionally or alternatively, thiscould include actively or passively sensing an effective resistanceand/or capacitance between the electrical contacts 640, 645 and furtherdetermining that the sensed resistance and/or capacitance corresponds tothe electrical contacts 640, 645 being in contact with skin. In someexamples, the instructions could include instructions to extract an ECGwaveform in response to a user input (e.g., in response to a userdepressing a button of the wearable device 600 to indicate that thewearer is contacting the first and second electrical contacts 640, 645to skin at appropriate respective first and second skin locations).

Other instructions in the program instructions 672 relating to the useof the signal conditioner 630 to extract one or more ECG waveforms fromvoltage fluctuations between the electrical contacts 640, 645 areanticipated. The program instructions 672 could include instructions toextract a plurality of ECG waveforms during a plurality of periods oftime using the signal conditioner 630. The program instructions 672could include instructions to log or otherwise store data related to theextracted ECG waveform(s) in the parameters and user data 874 and/orsome other data storage.

The instructions could include instructions to operate the wearabledevice 600 based on an extracted ECG waveform(s) and or informationrelated to extracted ECG waveform(s). For example, the instructionscould describe how to determine a health or other state of a wearerbased on extracted ECG waveform(s) (e.g., based on a determined heartrate, a determine pulse timing variability, a determined Q-T interval,determined QRS complex parameters, or some other determined property orfeature of one or more extracted ECG waveforms). The instructions coulddescribe how to determine whether the first and second electricalcontacts 640, 645 are in contact with skin and/or that an ECG waveformcan be extracted from voltage fluctuations between them 640, 645. Theinstructions could further describe how to operate the wearable device600 relative to such a determination. For example, one or more elements(e.g., a voltage or current sensor, an amplifier) of the signalconditioner 630 and/or of the wearable device 600 could be disabledand/or operated in a low-power state when the wearable device 600determines that the first and second electrical contacts 640, 645 arenot in contact with skin and/or that an ECG waveform cannot be extractedfrom voltage fluctuations between them 640, 645. Other operationsrelative to such a determination are anticipated and could be describedby the program instructions 672.

The program instructions 672 stored on the computer readable medium 660could include instructions for operating components of the wearabledevice 600 (e.g., the signal conditioner 630) to recharge therechargeable battery 635 and/or to power the wearable device 600 usingthe rechargeable battery 635. For example, the instructions couldinclude instructions for operating switches or other electricalcomponents to gate power from the electrical contacts 640, 645 to therecharger and/or from the recharger to the rechargeable battery 635.Additionally or alternatively, the instructions could includeinstructions to operate a voltage or current sensor (possibly a sensorof the signal conditioner 630) to detect the presence of an externalcharger in electrical contact with the electrical contacts 640, 645and/or to detect a charge state of the rechargeable battery 635. Arecharger and/or rectifier elements of the signal conditioner 630 or ofother electronics of the wearable device 600 could be passive, that is,they could be configured to recharge the rechargeable battery 635 and/orpower the wearable device 600 without direct operation by theprocessor(s) 650 or other elements of the wearable device 600 (otherthan the electrical contacts 640, 645) when the wearable device 600 ismounted to an external charger or other appropriately configured powersource. Additionally or alternatively, a coil and other components of awireless charger of the wearable device 600 could be configured toreceive electromagnetic energy and to charge the rechargeable battery635 using the received electromagnetic energy.

The program instructions 672 can include instructions for operating theuser interface(s) 680. For example, the program instructions 672 couldinclude instructions for displaying data about the wearable device 600,for displaying an extracted ECG waveform or other information generatedby the wearable device 600 (e.g., a heart rate, a variability ofextracted ECG waveforms), or for displaying one or more alerts generatedby the wearable device 600 and/or received from an external system.Further, program instructions 672 may include instructions to executecertain functions based on inputs accepted by the user interface(s) 680,such as inputs accepted by one or more buttons disposed on the userinterface(s) 680.

Communication interface 690 may also be operated by instructions withinthe program instructions 672, such as instructions for sending and/orreceiving information via an antenna, which may be disposed on or in thewearable device 600. For example, the program instructions 672 couldinclude instructions to operate the communication interface 690 totransmit an extracted ECG waveform and/or information related to anextracted ECG waveform using the communication interface 690 (e.g.,using a wireless transmitter of the communication interface 690). Thecommunication interface 690 can optionally include one or moreoscillators, mixers, frequency injectors, etc. to modulate and/ordemodulate information on a carrier frequency to be transmitted and/orreceived by the antenna. In some examples, the wearable device 600 isconfigured to indicate an output from the processor 650 by modulating animpedance of the antenna in a manner that is perceivable by a remoteserver or other remote computing device.

In some examples, the communication interface(s) 690 could be operablycoupled to the electrical contacts 640, 645 and could be configured tocommunicate with an external system by using the electrical contacts640, 645. In some examples, this includes sending and/or receivingvoltage and/or current signals transmitted through the electricalcontacts 640, 645 when the wearable device 600 is mounted onto anexternal system such that the electrical contacts 640, 645 are inelectrical contact with components of the external system.

In some examples, extracted ECG waveforms, temperature measurements,wearer profiles, history of wearable device use, health stateinformation input by device wearers and generated recommendations andclinical protocols may additionally be input to a cloud network and bemade available for download by a wearer's physician. Trend and otheranalyses may also be performed on the collected data, such asphysiological parameter data and health state information, in the cloudcomputing network and be made available for download by physicians orclinicians.

Further, extracted ECG waveforms and/or health state data fromindividuals or populations of device wearers may be used by physiciansor clinicians in monitoring efficacy of a drug or other treatment. Forexample, high-density, real-time data may be collected from a populationof device wearers who are participating in a clinical study to assessthe safety and efficacy of a developmental drug or therapy. Such datamay also be used on an individual level to assess a particular wearer'sresponse to a drug or therapy. Based on this data, a physician orclinician may be able to tailor a drug treatment to suit an individual'sneeds.

In response to a determination by instructions contained in the programinstructions 672 that a medical condition is indicated, the wearabledevice 600 may generate an alert via the user interface 680. The alertmay include a visual component, such as textual or graphical informationdisplayed on a display, an auditory component (e.g., an alarm sound), atactile component (e.g., a vibration), and/or an electro-hapticcomponent (e.g., an electro-haptic stimulus delivered using theelectrical contacts 640, 645). The textual information may include oneor more recommendations, such as a recommendation that the wearer of thedevice contact a medical professional, seek immediate medical attention,or administer a medication.

V. Illustrative Methods for Operating a Wearable Device

FIG. 7 is a flowchart of a method 700 for operating a wearable device.The operated wearable device includes (i) a housing, (ii) a mountconfigured to mount the housing to a wrist location of a first arm of awearer, (iii) a first electrical contact disposed on the housing andconfigured to contact skin at a first external body surface when thehousing is mounted on the first external body surface, (iv) a secondelectrical contact that is configured to be contacted by skin of asecond body surface located on a second arm of the wearer, (v) a signalconditioner connected to the first and second electrical contacts andconfigured to extract an electrocardiographic (ECG) waveform formvoltage fluctuations between the first and second electrical contacts.

The method 700 includes mounting the wearable device to the wristlocation of the first arm of the wearer such that skin of the firstexternal body surface of the wrist location is in contact with the firstelectrical contact (710). This could include encircling the wrist of thewearer with a band, strap, or other encircling element of the mount.This could include operating a clasp, snap, or other securing elementsof the mount such that the wearable device is mounted to the wristlocation (e.g., securing two halves of a flexible strap of the mounttogether around the wrist of the wearer). In some examples, the mountincludes an adhesive, and mounting the wearable device to the wristlocation (710) includes activating, applying, and/or exposing theadhesive and adhering the wearable device to the wrist location.

The method 700 also includes placing skin of the second external bodysurface of a second arm of the wearer in contact with the secondelectrical contact (720). This could include the wearer contacting thesecond electrical contact with skin of one or more of a finger, hand,wrist, or forearm of the second arm. Placing skin of the second externalbody surface in contact with the second electrical contact (720) couldoccur at the initiative of the wearer, e.g., in response to the wearerhaving performed and/or being about to perform a strenuous task (e.g.,exercise), experiencing some symptoms (e.g., fatigue, nausea, vertigo,heart palpitations, orthostatic hypertension), having received and/orbeing about to receive a drug (e.g., having taken nitroglycerin).Additionally or alternatively, placing skin of the second external bodysurface in contact with the second electrical contact (720) could occurin response to an indication (e.g., a vibration, a sound, a visualindication on a display of the wearable device, an indication throughsome other device in communication with the wearable device) that thewearer should perform such an action to enable the extraction of an ECGwaveform by the wearable device.

The method 700 also includes using the signal conditioner of thewearable device to extract an ECG waveform from voltage fluctuationsbetween the first and second electrical contacts (730). This couldinclude sampling (e.g., using an ADC or other discrete-time device) avoltage between the first and second electrical contacts a plurality oftime during a plurality of respective points in time. This could includeamplifying, filtering, level-shifting, inverting, and/or performing someother operation on the voltage between the first and second electricalcontacts using, e.g., one or more amplifiers, filters, op-amps,resistors, inductors, capacitors, other electronic element(s), and/orcombinations thereof.

The method 700 for operating a wearable device could include additionalsteps relating to an extracted ECG waveform. In some examples, themethod 700 could include indicating the extracted ECG waveform and/orinformation related to the ECG waveform using a display disposed in thewearable device. In some examples, the method 700 could includewirelessly transmitting the extracted ECG waveform and/or informationrelated to the ECG waveform using a wireless transmitter disposed in thewearable device. For example, the wearable device could transmit anextracted ECG waveform to a remote system (e.g., a server or cloudservice accessible to a healthcare provider). In some examples, themethod 700 could include logging or otherwise storing the extracted ECGwaveform and/or information related to the ECG waveform using a datastorage disposed in the wearable device. In some examples, the method700 could include operating the wearable device based on the extractedECG waveform and/or information related to the ECG waveform. Forexample, the wearable device could be operated to generate an alert,send a transmission to a remote system, or some other action in responseto the extracted ECG waveform and/or information related to the ECGwaveform (e.g., if a Q-T interval of the extracted ECG waveform exceedsa threshold).

In another example, the method 700 could include determining whether thefirst and second electrical contacts are in contact with skin at thefirst and second external body surfaces, respectively. For example, themethod could include determining that electrical contacts are contactingrespective skin locations based on a detected capacitance and/orresistance between the electrical contacts being within a specifiedrange and/or increasing or decreasing at a specified rate. The methodcould further include operating the wearable device relative to such adetermination. For example, extracting an ECG waveform using the signalconditioner (730) could be performed in response to the determinationthat the first and second electrical contacts are in contact withrespective first and second external body surfaces. Other applicationsof a determined resistance and/or capacitance are anticipated.

In some examples, the wearable device could include means for opticallydetecting the volume of blood in a portion of subsurface vasculature ofthe wearer at a plurality of points in time, and generating a bloodvolume waveform over time (i.e., a photoplethysmographic waveform) basedon the plurality of detected volumes of blood. An individual such bloodvolume detection could include operating a light source of the wearabledevice to emit light into the portion of subsurface vasculature throughoverlying skin and operating a light sensor of the wearable device toreceive light responsively reflected, scattered, or otherwise emittedfrom the portion of subsurface vasculature through the overlying skin.The method 700 could further include using the generated blood volumewaveform, in combination with the extracted ECG waveform, to determine ablood pressure of the wearer, a degree of atherosclerosis of thevasculature of the wearer, or some other health or medical state of thewearer. This could include determining time differences or othercomparisons of features of the extracted ECG waveform and the generatedblood volume waveform (e.g., a time difference between a maximum of thevolume waveform and a corresponding QRS complex of the ECG waveform) todetermine a flow rate, a pressure wave speed and/or latency, or otherinformation about the blood in the portion of subsurface vasculatureand/or information about the heart and vasculature of the wearer.

The example method 700 illustrated in FIG. 7 is meant as anillustrative, non-limiting example. Additional or alternative elementsof the method and additional or alternative components of the wearabledevice are anticipated, as will be obvious to one skilled in the art.

IV. Conclusion

Where example embodiments involve information related to a person or adevice of a person, the embodiments should be understood to includeprivacy controls. Such privacy controls include, at least, anonymizationof device identifiers, transparency and user controls, includingfunctionality that would enable users to modify or delete informationrelating to the user's use of a product.

Further, in situations in where embodiments discussed herein collectpersonal information about users, or may make use of personalinformation, the users may be provided with an opportunity to controlwhether programs or features collect user information (e.g., informationabout a user's medical history, social network, social actions oractivities, profession, a user's preferences, or a user's currentlocation), or to control whether and/or how to receive content from thecontent server that may be more relevant to the user. In addition,certain data may be treated in one or more ways before it is stored orused, so that personally identifiable information is removed. Forexample, a user's identity may be treated so that no personallyidentifiable information can be determined for the user, or a user'sgeographic location may be generalized where location information isobtained (such as to a city, ZIP code, or state level), so that aparticular location of a user cannot be determined. Thus, the user mayhave control over how information is collected about the user and usedby a content server.

The particular arrangements shown in the Figures should not be viewed aslimiting. It should be understood that other embodiments may includemore or less of each element shown in a given Figure. Further, some ofthe illustrated elements may be combined or omitted. Yet further, anexemplary embodiment may include elements that are not illustrated inthe Figures.

Additionally, while various aspects and embodiments have been disclosedherein, other aspects and embodiments will be apparent to those skilledin the art. The various aspects and embodiments disclosed herein are forpurposes of illustration and are not intended to be limiting, with thetrue scope and spirit being indicated by the following claims. Otherembodiments may be utilized, and other changes may be made, withoutdeparting from the spirit or scope of the subject matter presentedherein. It will be readily understood that the aspects of the presentdisclosure, as generally described herein, and illustrated in thefigures, can be arranged, substituted, combined, separated, and designedin a wide variety of different configurations, all of which arecontemplated herein.

What is claimed is:
 1. A wearable device, comprising: a housing; amodular mount for mounting the housing to a first external body surface,wherein the first external body surface is a wrist location of a firstarm of a wearer, wherein the modular mount comprises a band and a frame,wherein the housing is removably seated in the frame, and wherein theband can encircle a wrist of the first arm of the wearer; a firstelectrical contact disposed on the housing, wherein the first electricalcontact contacts skin at the first external body surface when thehousing is mounted on the first external body surface; a secondelectrical contact disposed on an outside surface of the modular mount,wherein the second electrical contact can be contacted by skin of asecond external body surface, wherein the second external body surfaceis a location of a second arm of the wearer; and a signal conditionerdisposed in the housing and electrically connected to the first andsecond electrical contacts, wherein the signal conditioner extracts anelectrocardiographic waveform from voltage fluctuations between thefirst electrical contact and the second electrical contact; wherein thesignal conditioner is in electrical contact with the second electricalcontact when the housing is seated in the frame, and wherein unseatingthe housing from the frame removes electrical contact between the signalconditioner and the second electrical contact.
 2. The wearable device ofclaim 1, wherein the signal conditioner is in electrical contact withthe second electrical contact via at least one spring-loaded contact,wherein the spring loaded contact is disposed in the wearable devicesuch that it is compressed when the housing is seated in the frame. 3.The wearable device of claim 1, further comprising a display, whereinthe display is disposed on an outside surface of the housing, andwherein the second electrical contact is disposed proximate to aperipheral edge of the display and at least partially encircles thedisplay.
 4. The wearable device of claim 1, wherein the secondelectrical contact is disposed on an outside surface of the band.
 5. Thedevice of claim 1, wherein at least one of the first and secondelectrical contacts has a surface comprising silver/silver-chloride. 6.The device of claim 1, wherein at least one of the first and secondelectrical contacts capacitively couples to skin at the first and secondlocations, respectively.
 7. The device of claim 1, further comprising awireless transmitter that transmits data related to the extractedelectrocardiographic waveform.
 8. The device of claim 1, furthercomprising a data storage that logs data related to the extractedelectrocardiographic waveform.
 9. The device of claim 1, wherein thesignal conditioner comprises at least one amplifier, at least onehigh-pass filter, and at least one low-pass filter.
 10. The device ofclaim 9, wherein the signal conditioner comprises fast recoverycircuitry, wherein the fast recovery circuitry detects when the signalconditioner is electronically saturated and responsively controls one ormore properties of the signal conditioner to reduce the electronicsaturation of the signal conditioner.
 11. The device of claim 1, furthercomprising a further sensor.
 12. The device of claim 11, wherein thefurther sensor comprises a light source and a light sensor, and whereinthe further sensor detects a volume of blood in subsurface vasculatureby emitting light into the subsurface vasculature through an overlyingskin location and receiving light from the subsurface vasculaturethrough the overlying skin location.
 13. The device of claim 1, whereinthe signal conditioner determines whether the first and secondelectrical contacts are in contact with skin at the first and secondexternal body surfaces, respectively.
 14. A method comprising: mountinga wearable device to a wrist of a first arm of a wearer, wherein thedevice comprises: a housing; a modular mount, wherein the modular mountcomprises a band and a frame, wherein mounting the wearable device tothe wrist comprises removably seating the housing in the frame andencircling the band around the wrist; a first electrical contactdisposed on the housing, wherein the first electrical contact contactsskin at a first external body surface when the wearable device ismounted to the wrist; a second electrical contact disposed on an outsidesurface of the modular mount, wherein the second electrical contact canbe contacted by skin of a second external body surface, wherein thesecond external body surface is a location of a second arm of thewearer; and a signal conditioner disposed in the housing andelectrically connected to the first and second electrical contacts,wherein the signal conditioner extracts an electrocardiographic waveformfrom voltage fluctuations between the first electrical contact and thesecond electrical contact; wherein removably seating the housing in theframe causes the signal conditioner to be in electrical contact with thesecond electrical contact, and wherein unseating the housing from theframe removes electrical contact between the signal conditioner and thesecond electrical contact; while the wearable device is mounted to thewrist location of the first arm of the wearer such that the firstelectrical contact is in contact with skin at the first external bodysurface, placing skin of the second external body surface in contactwith the second electrical contact; and while the first electricalcontact is in contact with skin at the first external body surface andthe second electrical contact is in contact with skin of the secondexternal body surface, using the signal conditioner to extract theelectrocardiographic waveform.
 15. The method of claim 14, furthercomprising indicating information related to the extractedelectrocardiographic waveform using a display disposed in the wearabledevice.
 16. The method of claim 14, wherein the device further comprisesa wireless transmitter, and further comprising: transmitting datarelated to the extracted electrocardiographic waveform using thewireless transmitter.
 17. The device of claim 14, wherein the devicefurther comprises a data storage, and further comprising: logging datarelated to the extracted electrocardiographic waveform using the datastorage.
 18. The method of claim 14, wherein the device furthercomprises a light source and a light sensor, and further comprising:operating the light source to emit light into subsurface vasculature ofthe wearer through an overlying skin location of the wearer; operatingthe light sensor to receive light from the subsurface vasculaturethrough the overlying skin location; determining a photoplethysmographicsignal related to the volume of blood in the subsurface vasculaturebased at least on the light received from the subsurface vasculature bythe light sensor; and determining a blood pressure of the wearer basedat least on the determined photoplethysmographic signal and theextracted electrocardiographic waveform.
 19. The method of claim 14,wherein the signal conditioner can further determine whether the firstand second electrical contacts are in contact with skin at the first andsecond external body surfaces, respectively, and further comprising:determining, using the signal conditioner, that the first and secondelectrical contacts are in contact with skin at the first and secondexternal body surfaces, respectively.
 20. The method of claim 14,wherein removably seating the housing in the frame causes the signalconditioner to be in electrical contact with the second electricalcontact via at least one spring-loaded contact, wherein the springloaded contact is disposed in the wearable device such that it iscompressed when the housing is seated in the frame.